The present invention relates to an improved wad for shotgun shell or so-called shot shell cartridges for hunting and shooting arms, and more particularly, to an improved cushioning and sealing structure of such wad.
Known shotgun cartridges for hunting use include a case or tubular envelope, usually of plastic material, closed at its lower end with a metal base and, at its upper end, by what is known as a star crimp. Inside the tubular, cylindrical envelope is a so-called wad of plastic material, usually extending along about the whole length of the cartridge. Such wad consists of a cushioning base or lower end providing a seat which covers the powder charge and, at its upper end, a bowl or cup for lead shot.
More particularly, several functions are fulfilled by wads of the above-mentioned type. In summary, these functions include carrying out a sealing action with respect to the shotgun barrel, containing the mass of the lead shot and protecting against frictional movement of the shot along the barrel, and also protecting against infiltration through the shot of the hot gases of burning powder, as well as damping or reducing the recoil effect upon firing of the gun.
Known wads, as heretofore used, generally include also a cushioning structure, which, in essence, comprises a substantially tubular element positioned between the shot cup or bowl and the seat covering the powder charge. The tubular element may have circular section, and is lozenged, multi-lozenged, or may include superimposed multitubular elements or the like which, because of flattening upon shooting, give rise to the cushioning effect.
In the embodiment disclosed in German Patent Specification No. 2 708 352, there is disclosed a wad system providing a cushioning structure comprising substantially flat, parallel portions lying at planes which are spaced from each other and perpendicular with respect to the cartridge axis. The aforementioned flat portions, being preferably disk-shaped, are spaced from each other and joined by connecting staggered walls which act as struts or stiff rods between the flat portions. Upon shooting, the explosive thrust against such wad causes the above-mentioned structure to be flattened, the flat portions being deformed according to a substantially sinusoidal configuration which is caused by said struts. Cartridges of this type present some drawbacks, particularly with respect to sealing conditions in that leakage of the propelling gas takes place between the wad and the internal wall of the shotgun barrel.
Such a sealing problem exists for conventional wads at the cartridge-case mouth at which location the main sealing element of the wad, namely the powder cup, must abruptly change its section when moving across the cartridge envelope rim in order to continue maintaining a sealing action against the barrel wall. Although carried out as rapidly as possible, such a change in section actually permits leakage, even if limited, of the propellant gases, to the detriment of full exploitation of the power of the propelling charge. This condition may be confirmed or evidenced by the fact that the upstream portion of a conventional wad, i.e., such portion of the wad as is located above the powder cup, shows an evident blackening due to such leakage of gases.
It should also be pointed out that the cushioning effect of known wads, e.g., as described in the above-mentioned German disclosure, does not provide any sealing action to prevent such gas leakage. Another problem arising from a conventional cartridge of this character is that there is not always a correct direction of the lead shot column.
An object of the present invention is the provision of a wad for shotgun cartridges for hunting and shooting arms which overcomes the above-noted limitations and drawbacks of the prior art, particularly, in that the present invention provides an improved type of wad that overcomes the problem of increasing the gas seal under compression for improving both the range and the accuracy of firing without increase of the friction with the shotgun barrel as would be detrimental to weapon effectiveness.
These and other objects are provided by the new wad for shotgun cartridges for hunting and shooting arms in accordance with the invention, as comprising a substantially cylindrical body of plastic material including a shot cup or bowl and a powder cup for confining the explosive and firing charge, the firing cup and shot cup being connected by a cushioning structure which provides additional sealing elements upstream of the firing cup, i.e., with respect to the advancement direction of the wad within the barrel, for avoiding explosion gas leakage.
According to further features of the invention, the cushioning structure comprises at least one additional sealing element wherein the latter is formed of a disk-shaped so-called tile of concave nature, the concavity of which is turned toward the powder cup and having a diameter such that when the tile is flattened upon firing, the diameter would be slightly greater than the inner diameter of the shotgun barrel. One side of the tile is connected to the shot cup or bowl, the other side being connected to the powder cup, and wherein the cushioning structure further comprises an axially connected rod between such tile and the powder cup.
According to a preferred embodiment of the present invention, the cushioning structure of the wad comprises at least two such tiles, each consisting of a disk-shaped element which is bent in tile-like character along one diameter, which diameter consequently represents the top edge of the tile, and wherein the tiles are reciprocally connected by walls which are outwardly inclined with respect to the cartridge base, the walls being preferably substantially perpendicularly positioned with respect to the inclined side portions of each such tile.
According to a further improvement of a wad of the invention, the powder cup is of semispheric shape, rather than having a flat bottom, and thus providing greater sealing action and a more uniform distribution of the forces on such powder cup, which thus act accordingly upon the wad during firing.
According to another characteristic of the present invention, the shot cup or bowl has a plurality of full thickness flutes directed along the generating lines of the shot cup, and including also vertical ribs which are spaced adequately apart and directed along the same generating lines.
In accordance with the further aspect of the wad of the invention, the diameter of the shot cup or bowl is less than that of the powder cup, and also of the tiles and such vertical ribs, reducing friction during movement of the wad along the shotgun barrel.
These and other characteristics wil be apparent from the following description describing a preferred embodiment of a wad in accordance with the invention, as illustrated by way of example and not of limitation in the drawing figures.